Hyperthermia for cancer treatment has been investigated mostly for superficial tumors and has been found to be efficacious, especially in combination with radiation or chemotherapy. Heating deep-seated tumors with external microwave or radio frequency fields is technically very difficult because the fields have limited penetration depths. In the chest area, external ultrasound techniques have little application due to the reflections at bone and air interfaces. Certain tumor sites in hollow viscera and cavities can be treated with intracavity techniques. There will be an estimated 10,900 new cases and 9,800 deaths from esophageal cancer in the U.S.A. during 1991. Despite improvements in protocols, current therapies involving surgery, radiation and chemotherapy have not significantly improved the survival rate in the last several decades. Recent clinical reports from China and Japan show much improved tumor response and survival rate in patients treated with combined hyperthermia and external radiation. In these studies, RF and microwave heating techniques were used. Our goal is to improve the treatment results by combining intracavitary radiation and hyperthermia with external radiation. Intracavitary radiation has the advantage of localizing radiation but also causes ulceration due to high radiation dosage. Hyperthermia can potentiate the radiation effects and therefore reduces the required dose. Thus, the hypothesis is that combined intracavitary radiation and hyperthermia improve the treatment outcome. In this study, we propose to conduct Phase I/II trials to investigate the efficacy and safety of intracavitary hyperthermia and radiation. We have developed a small and flexible prototype esophageal multilumen polyurethane tube, which can accommodate six channels of temperature sensors or radiation seeds at the periphery, and a microwave antenna in the center of the tube. We are developing and constructing various dipole antennas to heat esophageal tumors at various lengths. Based on the heating patterns obtained by thermography, we will select appropriate antennas and study the temperature variations in animal models over a one hour treatment period. This information is essential for treatment control since tumor and normal tissue temperatures are difficult to measure without considerable risk to the patient. The results should enable us to estimate the tissue and tumor temperature by the temperatures measured in the multilumen tube. The bioheat transfer equation will be used to calculate temperature profiles for various normal and tumor blood flow conditions. Theoretical predictions will be compared with static phantom results (no blood flow) and with results inside the esophagus, the aim is to heat the esophageal mucosa to above 43o C. The animal studies will reveal the correlation of tissue temperature with that measured in the multilumen tube. These theoretical and animal results are necessary for the human Phase I/II trials.